Base Plate for Fastening a Rail on a Solid Ground and Fastening of a Rail

ABSTRACT

A base plate for fastening a rail to a fixed bottom support, there being formed in the base plate an opening, which runs from its upper side to its underside, for an eccentric sleeve, which eccentric sleeve is adjustable in rotation in the opening for a sleeve, about an axis of rotation defined by a fastening member inserted through the eccentric sleeve, to allow changes in the position of the base plate. In the opening for the sleeve are markers for indexing for fixing the position in rotation of the eccentric sleeve, the markers spaced from one another such that, an adjustment of the eccentric sleeve in rotation between two adjacent markers for indexing involves a step-by-step change in the position of the base plate by a defined amount.

The invention relates to a base plate for fastening a rail to a fixed bottom support, there being formed or moulded in the base plate an opening, which runs from its upper side to its underside, for an eccentric sleeve, which eccentric sleeve is adjustable in rotation in the opening for a sleeve, about an axis of rotation which is defined by a fastening member inserted through the sleeve, to allow a change to be made in the position of the base plate.

As well as this, the invention relates to a fastener for a rail, which fastener is produced by using a base plate of this kind.

Known in practice is a rail fastening system offered under the name “ECF” in which the rail stands on the supporting surface of a base plate made of steel. At its longitudinal sides which are aligned in the longitudinal direction of the rail which is to be fastened in place, the supporting surface is bounded by respective ribs against which the foot of the rail is guided laterally when in the fully installed state. The rib also acts as a mounting for a clamping bolt whose head seats by positive-fit in a receptacle formed or moulded in the rib and whose shank passes through the central loop of a W-shaped clamping clip in the direction pointing away from the upper side of the base plate. By means of a nut which is screwed onto the clamping bolt, the clamping clip is then braced against the base plate in such a way that a sufficiently high hold-down force is exerted on the given side of the foot of the rail by the free ends of the resilient arms of the clamping clip.

It is ensured in this case that a rail fastener formed by the ECF system has an adequate ability to yield when a railway vehicle travels over it by an elastic intermediate layer, which intermediate layer is arranged between the base plate and a carrier plate which rests on whatever is the solid support in the given case.

To enable the position of the rail to be adjusted to whatever track gauge is required in the given case, there are formed or moulded in the ECF system, in the regions of the base plate which project laterally beyond the supporting surface, respective openings for sleeves, which openings run from the upper sides of the regions to their undersides and have seated in them eccentric sleeves which are designed to form hold-down sleeves. At its end which is at the top in the installed position, the eccentric sleeve has, in this case, a projection in the form of a collar which extends round the circumferential face of the sleeve and which rests on the upper face of the base plate in the installed position. At the same time, the heightwise distance left between the underside of the projecting collar and that end of the eccentric sleeve which is at the bottom in the installed position is of a size such that the sleeve stands on the carrier plate in the fully installed state. Inserted through the opening for the eccentric sleeve in this case is a bolt which is screwed into an anchor inset into the fixed bottom support and which thus creates an axis of rotation for the sleeve. What is achieved by this design is on the one hand that the base plate is braced against the fixed bottom support with a defined hold-down force by means of the eccentric sleeve which acts as a hold-down device. On the other hand, the position of the base plate, and with it the rail standing on it, can be shifted in a direction at right angles to the longitudinal extent of the rail by turning the eccentric sleeve, in order to adjust the position of the rail to the track gauge required.

It is a disadvantage of the known ECF system for fastening a rail in place that it is difficult for the installer to check the length for which the rail, or rather the base plate carrying it, is adjusted when there is an adjustment of the eccentric sleeve. This makes complicated re-measurement necessary, something which is difficult to accomplish with the requisite accuracy under the generally rough conditions which exist on a construction site.

Against the above background, the object of the invention was to provide a base plate with which it is easily possible to make an adjustment of the track gauge by a given length, which adjustment is simple to check.

With regard to the base plate, the invention has achieved this object by designing the base plate in the manner defined in claim 1. Advantageous embodiments of a base plate according to the invention are specified in the claims which are referred back to claim 1 and they will be explained in detail in what follows.

With regard to the fastener, this object has been achieved by the fastener which is specified in claim 9. Advantageous embodiments of a fastener according to the invention are specified in the claims which are referred back to claim 9 and they will likewise be explained in detail in what follows.

In a base plate according to the invention, markers for indexing for fixing the position in rotation of the eccentric sleeve are formed in the opening for the sleeve. The markers for indexing are arranged in this case at a spacing from one another such that, allowing for the eccentricity of the axis of rotation of the eccentric sleeve which is inserted in the opening for the sleeve from the central longitudinal axis of the opening for the sleeve, an adjustment in rotation of the eccentric sleeve between two adjacent markers for indexing involves a step-by-step change in the position of the base plate by a defined amount.

The indexable locking of the eccentric sleeve to the base plate which fixes the given position in rotation of the eccentric sleeve may be performed by means of a shaped member formed on the eccentric sleeve which is compatible with the shape of the marker for indexing. Depending on the location of the shaped member in question and the configuration of the eccentric sleeve, the markers for indexing may for example be formed or moulded in the form of recesses into the edge region of the upper side of the base plate, which edge region surrounds the opening for the sleeve. This may for example serve a useful purpose when the eccentric sleeve takes the form of a hold-down sleeve which carries on its circumferential surface a projection which bears against the upper side of the base plate in the fully installed state. However, fixing which is particularly secure and safe against wear is obtained when the markers for indexing are formed or moulded in the circumferential wall of the opening for the sleeve.

Regardless of where they are arranged, the markers for indexing may take the form of recesses in groove form.

The markers for indexing may be arranged in a given pattern which is helpful in the given application. In this way, it may be useful under certain circumstances for the size of the stepped change in position from one marker for indexing to the next to increase following a given function, which size is fixed by the distance between two markers for indexing. However adjustability which is versatile and particularly easy for the installer to follow is obtained if the angular intervals between mutually adjacent markers for indexing are each sized in such a way that each adjustment in rotation of the eccentric sleeve seated in the opening for the sleeve involves a change of unvarying size in the position of the base plate.

It also helps to simplify operation if one of the markers for indexing is defined as the “zero position” which forms the starting point for the change in the position of the base plate when a fastener for a rail which is formed using the base plate is being installed.

Following the model provided by the prior art, the base plate which is provided in a system according to the invention may have on its upper side a supporting surface for the rail which is to be fastened in place, which supporting surface is bounded by respective supporting shoulders at its longitudinal sides which are aligned in the longitudinal direction of the rail which is to be fastened in place. To enable tolerances affecting the width of the foot of the rail to be compensated for or to provide additional adjustability for the track gauge in this case, at least one adapter piece may be provided, in a manner which is likewise known per se, to bridge the gap which exists in the installed state between the foot of the rail which is to be fastened in place and the given supporting shoulder.

A way of fixing the position of the base plate which operates safely and securely is obtained if there are formed or moulded in each of the two side portions of the base plate which extend laterally of the supporting surface an opening for an eccentric sleeve, which opening is provided with markers for indexing.

Producing the base plate from plastics material on the one hand achieves an appreciable saving in weight in comparison with base plates made of steel or cast iron. In addition, the use of plastics material is a simple way of enabling shapes to be formed on the base plate which cannot be reproduced in steel or similar materials. What may be considered as a plastics material for the production of the base plate is for example glass-fibre reinforced polyamide.

A fastener according to the invention for fastening a rail to a fixed bottom support comprises an eccentric sleeve which is inserted as a sliding fit in the opening for a sleeve associated with it in a base plate formed in accordance with the invention, a fastening member being provided which, when inserted through the opening for the eccentric sleeve, defines the axis of rotation of the eccentric sleeve. In accordance with the invention, the eccentric sleeve has in this case, in the region of its circumferential surface, a shaped member which, when the eccentric sleeve is inserted in the associated opening for a sleeve in the base plate, co-operates by positive-fit with one of the markers for indexing in the opening for a sleeve in such a way that the position in rotation of the eccentric sleeve in the opening for a sleeve is fixed. In this way, the position of the base plate can be adjusted without any problems in a way which can readily be followed by an installer on site, in such a way that an adjustment of the track gauge to an ideally correct size is obtained without any burdensome measurements.

It is of particular importance to a system according to the invention that in the installed state the base plate stands on an intermediate layer which is arranged between the base plate and the fixed bottom support. This enables to make use of the elasticity of an intermediate layer of comparably large volume to give the fastener produced by the system according to the invention, when a railway vehicle travels over it, a yield which, as exactly as possible, can be determined in advance.

The eccentric sleeve may take the form of a hold-down sleeve and may have a projection protruding from its circumferential surface which bears against the upper side of the base plate in the fully installed state, to ensure that a defined seating exists in the associated opening for a sleeve. In this case, the eccentric sleeve may be of a height which is greater than the thickness of the base plate in the region of the opening for a sleeve associated with the said eccentric sleeve. Because a fastening member to hold the base plate to the fixed bottom support is inserted through the opening of the hold-down sleeve, the fastening member creates an axis of rotation for the eccentric member. What the eccentric member inserted in the opening for a sleeve then does in this embodiment, in a way comparable to the prior art explained above, is to cause the base plate to be loaded only by a preset maximum force. This prevents the base plate from being damaged by errors at the time of installation particularly when the said base plate is made of plastics material. At the same time, the sleeve also ensures that the elastic intermediate layer is only compressed by the fastening member so far as is required to give it a secure and reliable grip. In this way, the elasticity which the elastic intermediate layer is required to provide is reliably available even in the fully installed state. The sliding fit which the sleeve has in its associated opening in the base plate ensures in this case that the base plate is able to follow unhindered any compression or expansion of the intermediate layer which occurs as a result of the loads applied when travel takes place over it.

On the one hand to ensure that the support which the rail has on the fixed bottom support is as even as possible, but on the other hand to also minimise the abrasive wear on the elastic intermediate layer, there is provided in addition in a fastening system according to the invention a carrier plate which is to be arranged between the intermediate layer and the fixed bottom support. This can if required be made of comparably thin steel sheet or of a sufficiently strong plastics material.

The carrier plate may have in this case, on its upper side adjacent the base plate, a projection which, like the projection on the base plate which points towards the fixed bottom support and which has already been described above, performs the function of a stop for the movement of the base plate when a railway vehicle travels over the rail. At the same time, the projection on the carrier plate may, if suitably configured, form a receptacle for the elastic intermediate layer. This is particularly true if the projection concerned extends along the edge of the intermediate layer for at least a sufficient proportion of the circumference of the latter or if an adequate number of separate projections which fix the position of the intermediate layer are arranged on the carrier plate.

The installation of a fastener according to the invention can be simplified by providing at least one clip which, for installation, holds together in a pre-assembled position a pack made up of the base plate, the intermediate layer situated below it and the carrier plate situated below the intermediate layer.

The invention will be explained in detail below by reference to drawings, which show an embodiment. In the drawings:

FIG. 1 is an exploded view of a system for fastening a rail in place.

FIG. 2 is a plan view of the system in the fully installed position.

FIG. 3 is a view of the system from one side, in the fully installed position, looking in the longitudinal direction of the rail.

FIG. 4 is a perspective view of the system from one side in the fully installed position.

FIG. 5 is a perspective view from above of a base plate and associated eccentric sleeves.

FIG. 6 is a perspective view from below of the base plate having eccentric sleeves inserted in it.

FIG. 7 is a perspective view of an eccentric sleeve.

FIG. 8 is a perspective view from below showing a first enlarged detail of the base plate.

FIG. 9 is a perspective view from below showing a second enlarged detail of the base plate.

The system 1 for fastening a rail S to a fixed bottom support 2 which is formed in the present case by a concrete sleeper (not shown) comprises a base plate 3 made of a plastics material, an intermediate layer 4 made of an elastically yielding material which is to be arranged below the base plate 3, a carrier plate 5 which is to be arranged, below the intermediate layer 4, on the fixed bottom support 2, four eccentric sleeves 6 a, 6 b, 6 c, 6 d which have associated with them respective fastening bolts 7 a, 7 b, 7 c, 7 d which act as fastening members, two resilient members 8 a, 8 b, two adapter pieces 9 a, 9 b, and two clamping bolts 10 a, 10 b.

Seen in plan, the base plate 3 made of plastics material is of an elongated bone-like shape. Its outer regions 3 a, 3 b which adjoin respective ones of its narrow sides are of a considerably greater width B in this case, measured in the direction of the longitudinal extent L of the rail S which is to be fastened in place, than its central region, the change in the width B from the narrower central region to the adjoining wide lateral regions 3 a, 3 b taking place along a continuous step-free path.

In the central region, there is formed or moulded on the upper side O of the base plate 3 a supporting surface 3 c which extends in the longitudinal direction L, which extends across whatever is the width B of the narrower central region of the base plate 3 in the given case, and which is bounded laterally relative to the narrow sides of the base plate 3 by respective shoulders 3 d, 3 e.

A dovetail-like projection 3 f which projects towards the shoulder 3 d, 3 e situated opposite is formed on each of the faces for contact of the shoulders 3 e, 3 d, which faces for contact are associated with the supporting surface 3 c. By a recess of complementary shape, respective ones of the adapter pieces 9 a, 9 b may be fitted onto this projection 3 f in order, if required, to bridge a gap between the latter and the foot F of the rail S which is placed on the supporting surface 3 c and in this way to ensure secure and reliable lateral guidance for the rail S.

Formed or moulded in the shoulders 3 d, 3 e, in a position which is closely adjacent to the supporting surface 3 c and central relative to the extent of the shoulders in the longitudinal direction L, are respective through-openings 3 g, 3 h which run from the upper side O of the base plate 3 to its underside U. Inserted through the through-openings 3 g, 3 h from the underside U of the base plate 3 are respective clamping bolts 10 a, 10 b which are configured after the fashion of a conventional hexagon-head bolt. The heads 10 c of the clamping bolts 10 a, 10 b are seated in this case in respective receptacles 3 i, 3 j which are formed or moulded in the underside U of the base plate 3 and which are arranged in the region of the mouths of respective ones of the through-openings 3 g, 3 h.

The receptacles 3 i, 3 j are each surrounded by a circumferential wall 3 k which is integrally connected to the base plate 3. In their respective circumferential surfaces associated with the receptacles 3 i, 3 j, there are formed on the circumferential walls 3 k six faces for contact 3 l which are distributed at equal angular intervals around the centres of the respective receptacles 3 i, 3 j and the length La of each of which, measured in the circumferential direction of the respective receptacles 3 i, 3 j, is less than half the length Ls of the side-faces 10 d of the bolt head 10 c. Formed or moulded in the given circumferential wall 3 k between each pair of adjacent faces for contact 3 l is a recess 3 m which recedes into the circumferential wall 3 k relative to the faces for contact 3 l. In the circumferential wall 3 k, there is formed or moulded in addition in this case, adjacent to one of the faces for contact 3 l which define each of the recesses 3 m, a load-relieving recess 3 n formed after the fashion of a groove, while the recess 3 m merges into the other face for contact which defines it at a relatively shallow angle.

The regular distribution of the faces for contact 3 l, recesses 3 m and load-relieving recesses 3 n belonging to the respective receptacles 3 i, 3 j, and their position and dimensions, are selected in such a way that, in the fully installed position (FIG. 8), the side-faces 10 d of the bolt head 10 c bear against respective ones of the faces for contact 3 l and each of the edges 10 e of the bolt head 10 c which are present between pairs of side-faces 10 d is arranged in the region of a load-relieving recess 3 n without being in contact with the given circumferential wall 3 k.

In the same way, in the region of the recesses 3 m there is no contact between the bolt head 10 c and the given circumferential wall 3 k, which means that it is only the faces for contact 3 l which receive the torques acting on the bolt head 10 c during installation and in practical operation. The bolt head 10 c is prevented from cutting into the material of the circumferential wall 3 k in the region of its edges 10 e in this way, and any damage to or destruction of the circumferential wall 3 k as a result of overloading is also prevented.

The base plate 3 is therefore able to withstand without any problems the torques which arise when the resilient members 8 a, 8 b, which take the form of a conventional c-shaped clamping clip, are being braced. For the resilient members 8 a, 8 b to be braced, they are placed on the base plate 3 in such a way that the threaded shanks of the clamping bolts 10 a, 10 b respectively associated with them pass through the centre loops of the resilient members 8 a and 8 b respectively and the free resilient arms of the resilient members 8 a, 8 b rest on the foot F of the rail. Then, by means of nuts 12 which are screwed onto the respective threaded shanks, the centre loops of the resilient members 8 a, 8 b are pressed towards the base plate 3 until an adequate hold-down force is exerted on the foot F of the rail.

In the region of each of its corners, there is formed or moulded in the base plate 3 an opening 3 o for a sleeve which runs from the upper side O of the base plate 3 to its underside U.

Seated in each of the four openings 3 o for sleeves is one of the eccentric sleeves 6 a-6 d which are produced from a sufficiently strong material which is able to slide well when paired with the material of the base plate 3. These eccentric sleeves 6 a-6 d have a through-opening 6 e which is eccentrically arranged relative to the centre axis Me of the given eccentric sleeve 6 a-6 d. Formed on the outer circumferential surface of each of the eccentric sleeves 6 a-6 d is a narrow indexable projection 6 f whose axis extends parallel to the centre axis Me and which extends for the full height He of each of the eccentric sleeves 6 a-6 d. The eccentric sleeves 6 a-6 d are designed in this case to act as hold-down sleeves, for which purpose they have, at their upper edge associated with the upper side O of the base plate 3, a projection 6 g which extends round in a circle after the fashion of a collar. In the fully installed state, the projection 6 g from the eccentric sleeves 6 a-6 d bears against the upper side O of the base plate 3.

The four openings 3 o for sleeves are each surrounded by a circumferential wall 3 p which is formed by the plastics material of the base plate 3. Formed or moulded in the circumferential wall 3 p at irregular angular intervals a are markers for indexing 3 q which take the form of grooves, and whose axes extend parallel to the centre axis Mh of the given opening 3 o for a sleeve, and whose shape is complementary to that of the indexable projection 6 f which is formed on each of the eccentric sleeves 6 a-6 d.

The markers for indexing 3 q and the openings 3 o for sleeves are each so designed in this case that the eccentric sleeves 6 a-6 d respectively associated with them are guided in them by their indexable projections 6 f as a sliding fit and with positive-fit, in such a way that the position in rotation of the eccentric sleeves 6 a-6 d in the openings 3 o for sleeves associated with them is fixed but at the same time a relative movement between the base plate and the given sleeve 6 a-6 d directed in the direction defined by the centre axis Me is possible without any problems.

When the system 1 is being installed, one of the fastening bolts 7 a-7 d is inserted through the through-opening 6 e in each of the eccentric sleeves 6 a-6 d and is screwed into the anchor 11 of plastics material which is inset into the fixed bottom support 2. In this way, the fastening bolts 7 a-7 d each create an axis of rotation about which the eccentric sleeve 6 a-6 d associated with them can be adjusted in rotation. Taking into account the eccentricity of the axis of rotation which is created in this way relative to the centre axis Mh of the given opening 3 o for a sleeve, the angular intervals a between the markers for indexing 3 q are of a size such that, when the base plate 3 is fully installed, each adjustment in rotation between two markers for indexing involves a displacement of the base plate 3 in a direction at right angles to the longitudinal extent of the rail S by a distance which is always of the same size. In this way, the angular intervals α may for example be so designed that each adjustment in rotation of the eccentric sleeves 6 a-6 d displaces the base plate 2 by one millimetre to allow the track gauge to be adjusted.

Integrally formed or moulded on the base plate 3, to extend round the edge of the base plate 3, is an apron-like projection 3 r which points away from the underside U. The projection 3 r acts as a stop for movements directed towards the fixed bottom support 2 which the base plate 3 makes when a railway vehicle (not shown) travels along the rail S standing on it.

Formed or moulded into the base plate 3, in that region of the underside U which is not occupied by the openings 3 o for sleeves and their circumferential walls 3 q or by the receptacles 3 i, 3 j, is a stiffening structure 3 s which is formed by ribs 3 t which intersect at right angles and by depressions 3 u which are arranged between them. The depressions 3 u are filled in this case with a moulding material T which is lightweight but dimensionally stable. The filling T of moulding material terminates in this case substantially flush with the free top of the ribs 3 t or projects beyond the top of the ribs for a distance of, typically, at least 2 mm, and there are thus no longer any sharp protruding edges of the ribs 3 t.

So that the rail S is also supported elastically directly against the base plate 3, an elastic layer 3 v which is composed of a permanently elastic plastics material is sprayed onto the supporting surface 3 c. Alternatively, it is also possible for the elastic layer 3 v to be formed by a pre-manufactured pad of elastic material which is placed down on the supporting surface 3 c and which is in particular adhesively bonded thereto.

When seen in plan, the elastic intermediate layer 4 is of a shape which corresponds to the area occupied by the stiffening structure 3. When the system 1 is in the fully installed state, the stiffening structure 3 therefore completely covers the intermediate layer 4. This being so, even under the load applied by a railway vehicle travelling along the rail S, the filling T of filling material which is present in the depressions 3 u of the stiffening structure 3 s ensures that the ribs 3 t of the stiffening structure 3 s do not cut into the intermediate layer 4. Instead, the base plate 3 is always supported on the elastic intermediate layer 4 over such a large area that an optimum resilient action is maintained in the long term.

The thin carrier plate 5 which rests on the fixed bottom support 2 serves to protect the elastic intermediate layer against abrasive wear and dirt and ensures that there is an even surface for it to rest on. To secure the elastic intermediate layer in place on the carrier plate 5, a projection 5 a which follows the outline shape of the elastic layer forms, on the upper side of the carrier plate 5, which upper side is associated with the base plate 3, a receptacle in which, when the system 1 is fully installed, the intermediate layer 4 is seated in positive-fit. In addition, the projection 5 a also acts in this case as a stop which sets a limit to the movements of the base plate directed towards the fixed bottom support 2 and which prevents any excessive compression of the elastic intermediate layer 4.

The elastic intermediate layer 4 is also protected against being too highly compressed when being installed by the fact that the height He of the eccentric sleeves 6 a-6 d, which are designed to act as hold-down sleeves and which stand on the carrier plate 5 in the fully installed state, is selected to be such that the base plate 3 is only pressed against the elastic intermediate layer 4 with a defined force even when the fastening bolts 7 a-7 d are fully tightened. If the force concerned is to be very low, the height He of an eccentric sleeve is selected to be one which corresponds to the thickness of the base plate 3 in the region of the openings 3 o for sleeves plus the thickness of the elastic layer in the relaxed installed state, less the thickness of the projection 6 g.

REFERENCE NUMERALS

-   α Angular intervals -   1 System for fastening a rail S in place -   2 Bottom support -   3 Base plate -   3 a, 3 b Outer regions of the base plate 3 -   3 c Supporting surface of the base plate 3 -   3 d, 3 e Shoulders of the base plate 3 -   3 f Projection -   3 g, 3 h Through-openings -   3 i, 3 j Receptacles in the base plate 3 -   3 k Circumferential wall -   3 l Face for contact -   3 m Recess -   3 n Load-relieving recess -   3 o Opening for sleeve -   3 p Circumferential wall -   3 q Marker for indexing -   3 r Projection -   3 s Stiffening structure -   3 t Rib -   3 u Depression -   3 v Elastic layer -   4 Elastic intermediate layer -   5 Carrier plate -   5 a Projection -   6 a-6 d Eccentric sleeves -   6 e Opening in sleeve -   6 f Indexable projection -   6 g Projection -   7 a-7 d Fastening bolts -   8 a, 8 b Resilient members -   9 a, 9 b Adapter pieces -   10 a, 10 b Clamping bolts -   10 c Bolt head -   10 d Side-face of bolt head 10 c -   10 e Edge of bolt head 10 c -   11 Anchor of plastics material -   12 Nut -   B Width of the base plate 3 at respective points -   F Foot of rail -   He Height -   L Longitudinal direction -   Me Centre axis of a given eccentric sleeve 6 a-6 d -   Mh Centre axis of a given opening 3 o for a sleeve -   O Upper side of the base plate 3 -   S Rail -   T Moulding material -   U Underside of the base plate 3 

1. A base plate for fastening a rail to a fixed bottom support, there being formed or moulded in the base plate an opening, which runs from an upper side of the base plate to an underside of the base plate, for an eccentric sleeve, which eccentric sleeve is adjustable in rotation in the opening for a sleeve, about an axis of rotation which is defined by a fastening member inserted through the eccentric sleeve, to allow a change to be made in the position of the base plate, wherein there are formed, in the opening for the sleeve, markers for indexing for fixing the position in rotation of the eccentric sleeve and in that the markers for indexing are arranged at a spacing from one another such that, allowing for the eccentricity of the axis of rotation of the eccentric sleeve from a central longitudinal axis of the opening for the sleeve, an adjustment of the eccentric sleeve in rotation between two adjacent markers for indexing involves a step-by-step change in the position of the base plate by a defined amount.
 2. The base plate according to claim 1, wherein the markers for indexing are formed or moulded in a circumferential wall of the opening for the sleeve.
 3. The base plate according to claim 1, wherein angular intervals between mutually adjacent markers for indexing are sized in such a way that each adjustment in rotation of an eccentric sleeve seated in the opening for a sleeve involves a change of unvarying size in the position of the base plate.
 4. The base plate according to claim 1, wherein one of the markers for indexing is defined as a “zero position” which forms a starting point for the change in the position of the base plate when a fastener for a rail which is formed using the base plate is being installed.
 5. The base plate according to claim 1, wherein the markers for indexing take the form of recesses in groove form.
 6. The base plate according to claim 1, wherein the base plate has on its upper side a supporting surface for the rail which is to be fastened in place, which supporting surface is bounded by respective supporting shoulders at its longitudinal sides which are aligned in a longitudinal direction of the rail which is to be fastened in place.
 7. The base plate according to claim 5, wherein there are formed or moulded in two side portions of the base plate which extend laterally of the supporting surface an opening for an eccentric sleeve, which opening is provided with markers for indexing.
 8. The base plate according to claim 1, wherein the base plate is made of plastics material.
 9. A fastener for fastening a rail to a fixed bottom support, having a base plate formed in accordance with claim 1, having an eccentric sleeve which is inserted as a sliding fit in the opening for a sleeve associated with it in the base plate, and having a fastening member which, when inserted through an opening of the eccentric sleeve, defines the axis of rotation of the eccentric sleeve, the eccentric sleeve having a circumferential surface, wherein the eccentric sleeve has, in the region of its circumferential surface, a shaped member which, when the eccentric sleeve is inserted in the associated opening for a sleeve in the base plate, co-operates by positive-fit with one of the markers for indexing in the opening for a sleeve in such a way that the position in rotation of the eccentric sleeve in the opening for a sleeve is fixed.
 10. The fastener according to claim 9, wherein an intermediate layer of an elastic material is arranged between the base plate and the fixed bottom support.
 11. The fastener according to claim 9, wherein the eccentric sleeve takes the form of a hold-down sleeve and has a projection protruding from its circumferential surface which bears against the upper side of the base plate in a fully installed state.
 12. The fastener according to claim 10, wherein a height of the eccentric sleeve is greater than a thickness of the base plate in a region of the opening for a sleeve associated with the said eccentric sleeve.
 13. The fastener according to claim 10, wherein a carrier plate is arranged between the elastic intermediate layer and the fixed bottom support.
 14. The fastener according to claim 13, wherein there is formed in the carrier plate a receptacle in which the elastic intermediate layer is situated.
 15. The fastener according to claim 11, wherein a height of the eccentric sleeve is greater than a thickness of the base plate in a region of the opening for a sleeve associated with the said eccentric sleeve. 